System for controlling the over-voltage or &#34;hot shot&#34; time on instant heating tubes



July 5, 1966 L. A. GLYNN SYSTEM FOR CONTROLLING THE OVER-VOLTAGE 0R 'HOT SHOT TIME ON INSTANT HEATING TUBES Filed Jan. 28, 1963 DETECTOR POWER SUPPLY m E GNU GRU TAIP HAEP ATT wP RLAP HLOU EOEU OPS VH INVENTOR LEON A. GLY/V/V ATTORNEY 3 259 793 SYSTEM FOR CONTIiGLiJING THE OVER-VOLT- AGE OR HOT SHOT TIME ON INSTANT HEAT- ING TUBES Leon A. Glynn, Cedar Rapids, Iowa, assignor to Collins Radio Company, Cedar Rapids, Iowa, a corporation of Iowa Filed Jan. 28, 1963, Ser. No. 254,246 5 Claims. (Cl. 315-86) This invention relates in general to tube circuits, and in particular to a method of quickly warming up a tube for operation. I

It has normally been necessary to operate radio receivers and transmitters with the filament voltages continuously on. This is because an appreciable time is required to bring a tube to an emitting temperature. For example, when two-way voice communication is being carried on, transmission occurs, the operator normally pushes a push-to-talk button on his microphone and starts to talk immediately. Thus, the push-to-talk microphone normally applies plate voltage to the transmitter tubes and the cathodes heaters have been on continuously. If the heater voltages had not been applied during receiving time, an appreciable time delay would occur before transmission could occur due to the lack of emission in the transmitter tubes until they had warmed-up.

Continuous application of heater power to the tubes results in high average power consumption which is particularly undesired in portable battery equipments. Since the transmitting cycle may be used less than of the United States Patent 0 time, the transmitter heater power is being wasted the other 90% of the time.

It an object of the invention, therefore, to provide a quick warm-up method for vacuum tubes. Another object of the invention is to provide a system in which heater current is supplied to tubes only when they are to be used.

A feature of the invention is found in the provision for a temperature detecting means mounted within a tube envelope and which operates in conjunction with a relay means such that an initial high heater power is applied so as to very quickly raise the temperature of the cathode to an emitting temperature, and then the heater is switched to a normal operating power by the detector within the tube. This results in an almost instantaneous emission from the tube so that almost no time delay exists when transmission occurs.

Further objects, features and advantages of the invention will become apparent from the following description and claims when read in view of the drawing in which:

The figure is a partial cutaway schematic view of the fast warm-up control of this invention.

The figure shows an electron tube designated generally as 10 which has a base supporting structure 11 which is attached to an envelope 12. Mounted within the tube is a plate 13 of generally cylindrical shape and one or more grids. By way of an example, a control grid 14 and a screen grid 16 are illustrated mounted within the envelope. A cathode cylinder 17 is mounted within the envelope such that the control grid and screen grids are between it and the plate, A center feed line 18 extends from the base 11 of the tube to the end 19 of the cylinder 17, and forms a part of the cathode heater circuitry Within the cathode cylinder 17 is mounted a cylindrical electrode 21 which is evenly spaced from the inside of the cylinder 17.

It is to be realized, of course, that the plate 13 and the grids 14 and 16 and the electrode 21 are insulated from each other and from the cathode structure comprising the cylinder 17 and the center feed 18. Suitable lead connections are attached to the plate 13 and grids 14 and 3,259,793 Patented July 5, 1966 16 in a conventional manner for operation of the tube. Since such connections do not form a part of the improvement of this invention, their detailed construction is not illustrated or shown. Such structures are well-known to those skilled in the art.

The time delay in the operation of a tube such as shown in the figure results is the time required for the cathode 17 to reach an emitting temperature so that electrons are available to be drawn toward the plate 13 and controlled by the grid structures. This heating time can be reduced by applying unusually high power to the cathode circuit until it has reached an operating temperature. However, if the unusually high power were not removed after the filament had reached an emitting temperature, the filaments would burn out.

The diode structure comprising the electrode 21 and the cathode cylinder 17 serves as a detector for determining when the temperature of the cathode has become high enough to allow emission, and in this invention the heater power to the cathode is switched from an initial high voltage to an operating voltage when the detector electrode 21 commences to receive emission from the cathode cylinder 17.

This is accomplished by having the cathode cylinder 17 grounded by the lead 22 at its lower end. Thus, the heater current flows from ground to cylinder 17 across the end 19 to the center lead in conductor 18 and to lead 23. Lead 23 is connected to the movable terminal 24 of a switch 26. Switch 26 has a pair of stationary contacts 27 and 28 which the movable contact 24 may be engaged. Stationary contact 27 is connected to an operating voltage heating supply 29 through a switch 39, and stationary contact 28 is connected to a high voltage power supply 31 through a switch 40. Both power supplies 29 and 31 have their opposite sides connected to ground to complete the circuit.

The diode electrode 21 is connected to a lead 32 which is connected to a detector power supply 33 through a resistor R and switch 41. Power supply 33 has one terminal connected to ground. A relay 34 has a movable armature 36 which controls the position of movable contact 24 of switch 26. A resistor R is connected in series with the relay winding 37 of relay 34. One end of the relay winding 37 is connected to ground. The other side of resistor R is connected to electrode 21 by the lead 32.

A push-to-talk switch 38 in addition to closing the transmitter energizes circuits in a conventional manner also connects power supplies 29, 31 and 33 to the tube heater and control circuits. Switches 39, 40 and 41 are respectively in the power lines leading to power supplies 29, 31 and 33 and a mechanical linkage 42 interconnects switches 29, 40 and 41 to push-to-talk switch 38.

In a particular system constructed according to this invention, the detector power supply 33 produces 150 volts. The power supply 29 provides 20 watts of power when connected to the filament, or 8 amps at 2% volts. The high voltage power supply 31 supplies watts of power to the filament, or 5 volts at 16 amps. The resistor R has 31,000 ohms impedance and resistor R has 8,000 ohms impedance. The impedance across the diode comprising electrode 21 and the cathode cylinder 17 varies from infinity when there is no emission at a time T to 1,000 ohms in milliseconds.

Thus, in operation the detector power supply is applied when the tube is to be used, and since the filament 17 is cold and produces no emission, the impedance across the diode will be infinite and the relay 34 will be energized moving the contact 24 to engagement with contact 28-. This will connect the high voltage power supply to the center conductor 18 and the filament 17. Within 140 milliseconds the filament 17 will have been heated to a temperature such that emission occurs and the impedance across the diode electrode 2]. to the inside of the filament 17 will have been reduced to 1,000 ohms. At this point, due to voltage divider action, the relay 34 will open and the movable contact 24 will move from engagement with contact 28 to engagement with contact 27 thus disconnecting the high voltage power supply 31 from the filament and connecting the operate power supply 29 to the filament, and operation will continue in this mode as long as the tube is being utilized.

If the tube is being used, in a transmitter for example, voice communication may occur after 140 milliseconds which does not interfere with voice conversation. When transmission is ended, the push-totalk switch 38 will be opened thereby disconnecting power supplies 29, 31 and 33 from the tube so that no power will be used until it is desired to transmit again.

It is seen that this invention provides a simple and convenient way of saving power, and eliminates the normal time delay.

Although the apparatus has been described with respect to preferred embodiments thereof, it is not to be so limited, as changes and modifications may be made therein which are within the full intended scope of the invention as defined by the appended claims.

I claim:

1. Means for quickly heating the cathode of an electron tube having a cathode comprising an electrode mounted adjacent the cathode, a voltage supply connected across the cathode and the electrode, a pair of heater power supplies selectably connected to the cathode, a switching means connected to the cathode and the pair of heater power supplies, a detector means connected to the diode formed by the cathode and the electrode, the detector means connected to the switching means so as to control connection of the pair of power supplies to the filament, and said detector means comprises a relay and a voltage divider circuit with its armature connected to the switching means.

2. An apparatus according to claim 1 where a first resistor is connected between the voltage supply and the electrode, and wherein the armature of the relay is connected in series with a second resistor which has its opposite side connected to the electrode.

3. Apparatus for quickly heating the filament of an electron tube comprising an electrode mounted adjacent the filament, the electrode connected to a pair of resistors, a detector power supply connected to the other side of one of the resistors, the other side of said detector power supply connected to ground, a relay with its energizing coil connected to the other side of the second resistor, the other side of said relay coil connected to ground, a single pole double throw switch with its movable contact controlled by the armature of the relay, the movable contact of the switch connected to the filament, an operate power supply and a high power supply connected respectively to stationary contacts of the switch, the opposite sides of said power supplies connected to ground, and the opposite side of said filament connected to ground.

4. In apparatus according to claim 3 three single pole switches connected in circuit with the detector power supply, the operate power supply and the high power supply, and an operate button connected to said three switches to close them.

5. In combination: an electron tube having at least a plate and a cathode the latter of which must be heated to a predetermined minimum temperature for operations, means adapting said cathode to be heated, and an additional electrode mounted adjacent to said cathode, said cathode and said additional electrode forming a diode for detecting when said predetermined operating temperature is reached, and in response thereto providing an output usable to reduce the heating rate of said cathode to thereby protect said tube against overheating.

References Cited by the Examiner UNITED STATES PATENTS 2,290,819 7/1942 Warshawsky 315-407 X DAVID J. GALVIN, Primary Examiner.

GEORGE WESTBY, Examiner.

R. JUDD, Assistant Examiner. 

1. MEANS FOR QUICKLY HEATING THE CATHODE OF AN ELECTRON TUBE HAVING A CATHODE COMPRISING AN ELECTRODE MOUNTED ADJACENT THE CATHODE, A VOLTAGE SUPPLY CONNECTED ACROSS THE CATHODE AND THE ELECTRODE, A PAIR OF HEATER POWER SUPPLIES SELECTABLY CONNECTED TO THE CATHODE, A SWITCHING MEANS CONNECTED TO THE CATHODE AND THE PAIR OF HEATER POWER SUPPLIES, A DETECTOR MEANS CONNECTED TO THE DIODE FORMED BY THE CATHODE AND THE ELECTRODE, THE DETECTOR MEANS CONNECTED TO THE SWITCHING MEANS SO AS TO CONTROL CONNECTION OF THE PAIR OF POWER SUPPLIES TO THE FILAMENT, AND SAID DETECTOR MEANS COMPRISES A RELAY AND A VOLTAGE DIVIDER CIRCUIT WITH ITS ARMATURE CONNECTED TO THE SWITCHING MEANS. 